

package com.hazelcast.function;

import javax.annotation.Nonnull;
import java.util.Map.Entry;

/**
 * Factory methods for several common functions.
 *
 * @since 4.0
 */
public final class Functions {

    private Functions() {
    }

    /**
     * Synonym for {@link FunctionEx#identity}, to be used as a
     * projection function (e.g., key extractor).
     *
     * @param <T> the type of the input and output objects to the function
     */
    @Nonnull
    public static <T> FunctionEx<T, T> wholeItem() {
        return FunctionEx.identity();
    }

    /**
     * Returns a function that extracts the key of a {@link Entry}.
     *
     * @param <K> type of entry's key
     */
    @Nonnull
    public static <K> FunctionEx<Entry<K, ?>, K> entryKey() {
        return Entry::getKey;
    }

    /**
     * Returns a function that extracts the value of a {@link Entry}.
     *
     * @param <V> type of entry's value
     */
    @Nonnull
    public static <V> FunctionEx<Entry<?, V>, V> entryValue() {
        return Entry::getValue;
    }
}
